Please enable JavaScript.
Coggle requires JavaScript to display documents.
gihep 14: post-absorption processing of carbs (carb digestion (mouth:…
gihep 14: post-absorption processing of carbs
carb digestion
mouth: salivary alpha amylase
stomach: inactivates salivary amylase
duodenum: pancreatic alpha amylase, isomaltase, maltase, lactase, sucrase
digested carbs go to liver (except cellulose)
absorption in duodenum + upper jejunum
gluconeogenesis
after hepatic glycogen stores depleted (10-18hrs fasting)
90% in liver, 10% in kidneys
substrates + lactate, pyruvate, glycerol, AAs
stimulated by glucagon, or absence of insulin
the Cori cycle
muscle: glucose -> lactate
liver: lactate -> glucose
glycogen
building block = UDP-glucose
stores
liver: maintains blood glucose
muscle: for contrations (ATP reserve)
rapidly mobilisable
significant but finite
alpha(1-4) bonds within chains, alpha(1-6) bonds join chains
glycogen synthesis
glycogen synthase forms alpha(1-4) bonds @ non-reducing ends
elongation
branching enzyme forms alpha(1-6) bonds (branch points)
glycogenin = protein primer, accepts glucose to form a new chain
glycogen breakdown
glycogen phosphorylase cleaves alpha(1-4) bonds, releasing G1P
stops 4 glucose residues before each branch point, forming a limit dextrin
debranching enzyme cleaves alpha(1-6) bonds
G1P converted by phosphoglucomutase to G6P
in muscle G6P goes directly into glycolysis
G6P converted to glucose by G6 phosphatase + G6 translocase
only happens in liver
glycogen metabolism regulation
1) allosteric
G6P activates synthase + deactivates phosphorylase
muscle contractions release Ca2+, activating phosphorylase
high AMP and low ATP in muscle activates phosphorylase
2) hormonal
MOA: reversible phosphorylation + dephosphorylation
synthase active when dephosphorylated
phosphorylase active when phosphorylated
glucagon, adrenaline + protein kinases phosphorylate
insulin + phosphatase dephosphorylate
glycogen storage disorders
genetic
defect in genes for enzymes of glycogen metabolism
abnormal accumulation,synthesis,degradation
affect liver + muscle
no5: McArdle Disease
muscle glycogen phosphorylase deficiency
muscle fatigue, myoglobinuria
no1: Von Gierke's disease
G6 phosphatase deficiency
25% of GSDs
incidence = 1 in 100 000
normal glycogen structure , just increased storage
hypoglycaemia, lactic acidosis, ketosis
treatment = glucose infusions